Aldose reductase (AR), the first enzyme of the polyol pathway, has been implicated in the secondary complications of diabetes. We have been involved in characterizing the structure of the protein and gene for AR and in determining the regulatory mechanism that induces AR in hypertonic cell culture systems. The purpose of this research is to use our knowledge of the structure and cellular regulation of AR to design an innovative generation of inhibitors targeting either the protein or the gene and its gene products. Our laboratory has determined the amino acid sequence and gene sequence of rat AR. Recently, we used a transient expression assay to demonstrate that our rat AR gene promoter is functional. Other areas of research have included the expression of rat lens and human placenta recombinant AR in Escherichia coli. Immunological and kinetic data indicate that these recombinant proteins are very similar to their tissue counterparts. The only observed difference is a slight shift in the pI of 0.2 pI units. The more basic nature of these recombinant proteins may be due to their lack of acetylation, which was observed through chemical sequencing. Studies are now under way to localize important binding sites on the recombinant protein, such as the NADPH, substrate, and inhibitor binding sites. We have also been interested in the regulation of AR. Our cell culture studies using several cell types, including human lens and human retinal pigmented epithelial cells, show that AR can be induced from 8- to 30-fold when these cells are grown in hypertonic conditions. Studies on the gene promoter are now being conducted to pinpoint the regulatory elements responsive to hypertonicity. It appears that 1 kb of 5' flanking sequence is not sufficient for increased transcriptional activity when cells are exposed to hypertonic conditions. By knowing the gene structure and using this hypertonic cell culture amplification system, we can begin studies on the inhibition of AR at the gene or mRNA level.